[JSC] The line starts of a source come with its code, and positions are kept - #734
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…ly it, and positions are kept A line and column come from the source's LineStartTable, which scans the whole source the first time it is asked. For code that runs from cached bytecode nothing else reads the text, so the first stack trace pages all of it in. - The table holds line lengths as LEB128 with a checkpoint every 64 lines, in place of a 32-bit offset per line. - LineStartTable::encode() gives an embedder those bytes to store beside the text, and SourceProvider::setEncodedLineStarts() takes them back. The text is then never scanned. - documentLineColumnForOffset() no longer computes the end of the line, which read the text. - ExpressionInfo::lineColumnForInstPC() keeps each position it computed. Every lookup decoded the expression info from the start of its chapter. Unlinked code is shared by sources with the same text, so an entry records the source and offset it was computed for.
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Beyond the inline findings, I also checked two things that turned out fine: the new m_cachedLineColumns member in the placement-new'd ExpressionInfo slab is covered by totalSizeInBytes (it uses sizeof(ExpressionInfo)) and is destroyed through the unique_ptr default deleter, so the map's table is neither overlapped by the payload nor leaked; and the LEB128 writer in build() and the reader in walk() agree on byte order and continuation bit, with lineEndFor only calling startOfLine(line0Based + 1) when that line exists.
Extended reasoning...
The change replaces LineStartTable's per-line offset vector with a LEB128-plus-checkpoint byte encoding in Source/JavaScriptCore/parser/SourceProvider.{h,cpp}, adds an embedder-supplied table path, and adds an unsynchronized per-ExpressionInfo line/column memo used from CodeBlock::lineColumnForBytecodeIndex. It touches no auth, crypto or injection surface, but the externally supplied table is parsed with raw pointer walks. Inline findings on thread safety, unvalidated external bytes, unbounded cache growth and the new test's runtime are already posted, so a human look is needed regardless; this note only records what else was examined and ruled out.
Findings marked 🟡 are optional suggestions and need no follow-up push.
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Included review availability: This review used your included allowance. 3 included reviews remain after this review. Your included PR review attempts over the past 7 days set your current allowance at 5 reviews per hour. WalkthroughThe change replaces per-line start offsets with a compact encoded table. The parser collects line starts, and code caches preserve them. Bytecode and builtin position lookups use line-and-column data. Stress tests cover reported positions across line terminators, source lengths, and line counts. ChangesSource Position Handling
Priority: ➖ Normal Merge Risk: 🔵 Low · up to The position-handling changes have two unresolved bounds concerns. Confirm them against the reviewed head before relying on the affected embedder and builtin paths. 🚥 Pre-merge checks | ✅ 3 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (3 passed)
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Inline comments:
In `@Source/JavaScriptCore/bytecode/ExpressionInfo.cpp`:
- Around line 898-908: Protect all accesses to m_cachedLineColumns in
ExpressionInfo::lineColumnForInstPC with a Lock, including the lookup and
insertion, so concurrent calls cannot race on the map.
In `@Source/JavaScriptCore/parser/SourceProvider.cpp`:
- Around line 277-281: Update LineStartTable::setEncoded to validate the encoded
size against the block count and ensure each block stream offset is within the
stream; if validation fails, ignore the supplied data and use encode(text).
Bound decoding in EncodedLineStarts::walk with an end pointer, stopping before
reading past the stream or continuing an unterminated LEB128 value.
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JSTests/stress/line-start-table-positions.jsSource/JavaScriptCore/bytecode/CodeBlock.cppSource/JavaScriptCore/bytecode/ExpressionInfo.cppSource/JavaScriptCore/bytecode/ExpressionInfo.hSource/JavaScriptCore/bytecode/UnlinkedCodeBlock.cppSource/JavaScriptCore/bytecode/UnlinkedCodeBlock.hSource/JavaScriptCore/parser/SourceProvider.cppSource/JavaScriptCore/parser/SourceProvider.h
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…e has in common The cache held the final line and column, which depend on where the source says its text starts, in unlinked code that sources share. So each entry had to record the source it was for, and two sources that shared code evicted each other. It now holds the line and column in the text. Code is shared through the CodeCache only, which is keyed by the text of a whole source, so that position is the same for all of them, and the only miss is the first time an instruction is asked about. The caller adds the start position. - A lock guards the map: with Options::useSourceCodeDump() the compiler threads ask for positions too. - The new test computes what it expects in one pass and uses each long line once. It took 7 seconds and takes 0.03.
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Nothing blocking. The comments below are optional suggestions. There is no need to push a fix for them before merging.
The second commit addresses the lock, the source-ID keying and the test's run time from the earlier pass; beyond the one inline nit, I also checked that the new Lock/HashMap members never reach the bytecode cache (CachedExpressionInfo packs payload() only, so the format is unchanged) and that the map is released through the unique_ptr destructor. The cache now relies on CodeCache sharers having the same text before sourceOffset: SourceCodeKey compares only the substring, and I found no JSC caller that hands a top-level SourceCode with a nonzero startOffset to the CodeCache, but Bun-side constructors are not visible from this checkout, so that assumption is worth a look from someone who knows them.
Extended reasoning...
Since the prior review, commit 5cdec80 added a Lock around ExpressionInfo::m_cachedLineColumns, dropped provider.asID() from the cache by caching the zero-based line/column in the text keyed on InstPC only, and rewrote the test's expected-position pass to be O(n). The findings-present note records what was examined beyond the inline nit: bytecode cache serialization is unaffected because CachedExpressionInfo::pack copies payload() rather than the object, and ExpressionInfo is owned by std::unique_ptr so the HashMap buffer is freed. The remaining unverified assumption is that every SourceCode sharing an UnlinkedCodeBlock through the CodeCache has the same provider text before its sourceOffset; SourceCodeKey::operator== compares string() (the substring), and within JSC all top-level SourceCodes are built at offset 0, but embedder (Bun) construction sites cannot be checked here.
A source's line start table was built by a scan of the whole text, the first time a position in it was asked for, unless an embedder supplied it. Whoever makes the code now makes the table. - The lexer collects the line starts while it parses. The first parse of a source is of all of it, or of a function that is nearly all of it, and what it does not read is scanned. - The code has them too, like the sourceURL directive: the top-level unlinked code, its record in the bytecode cache, and the cache entry of an embedder's builtin. A source that is not parsed, because the code came out of the CodeCache or out of bytecode, gets them from there. In the bytecode they are with the expression info, and are borrowed from a payload that stays mapped. - A source under 1,024 characters does without, until it is asked for a position: a table has a fixed cost, which is 3% of what it takes to evaluate 100 characters. A source of one line never allocates. - So an embedder has nothing to supply: LineStartTable::encode() and SourceProvider::setEncodedLineStarts() are gone. - BuiltinsSourceProvider is the text of many builtins, one after the other. A position in it counts from where its builtin starts, as it did when a SourceCode had a first line, and takes no table. An error in Array.prototype.map was at line 3323, and is at line 1 again. - The map in ExpressionInfo has no lock. The three callers that run beside the mutator, all under Options::useSourceCodeDump(), use CodeBlock::lineColumnForBytecodeIndexConcurrently(), which keeps nothing. The collector asks only while the mutator is stopped. - A lookup in a table that is built takes no lock. - The lengths are decoded with WTF::LEBDecoder. line-start-table-not-built-by-ordinary-parse.js said that a parse leaves no table. line-start-table-comes-from-the-parse.js takes its place, and runs through the bytecode cache too.
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…parse alone With the bytecode cache configuration every program has to be in the cache in the second run, and one that does not compile is never cached, so loadString() of it crashed there. checkModuleSyntax() only parses.
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Inline comments:
In `@Source/JavaScriptCore/parser/SourceProvider.cpp`:
- Around line 344-350: Update BuiltinsSourceProvider::lineColumnInTextForOffset
to clamp offset to source().length() before finding the line start and scanning,
while preserving the existing line-column calculation for in-range offsets.
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JSTests/stress/builtin-position-counts-from-the-builtin.jsJSTests/stress/line-start-table-comes-from-the-parse.jsJSTests/stress/line-start-table-not-built-by-ordinary-parse.jsJSTests/stress/line-start-table-positions.jsSource/JavaScriptCore/Scripts/tests/builtins/expected/JavaScriptCore-Builtin.Promise-Combined.js-resultSource/JavaScriptCore/Scripts/tests/builtins/expected/JavaScriptCore-Builtin.prototype-Combined.js-resultSource/JavaScriptCore/Scripts/tests/builtins/expected/JavaScriptCore-BuiltinConstructor-Combined.js-resultSource/JavaScriptCore/Scripts/tests/builtins/expected/JavaScriptCore-InternalClashingNames-Combined.js-resultSource/JavaScriptCore/Scripts/wkbuiltins/builtins_generate_combined_implementation.pySource/JavaScriptCore/builtins/BuiltinExecutables.cppSource/JavaScriptCore/builtins/BuiltinExecutables.hSource/JavaScriptCore/bytecode/CodeBlock.cppSource/JavaScriptCore/bytecode/CodeBlock.hSource/JavaScriptCore/bytecode/ExpressionInfo.cppSource/JavaScriptCore/bytecode/ExpressionInfo.hSource/JavaScriptCore/bytecode/UnlinkedGlobalCodeBlock.hSource/JavaScriptCore/dfg/DFGJITCompiler.cppSource/JavaScriptCore/ftl/FTLCompile.cppSource/JavaScriptCore/jit/JIT.cppSource/JavaScriptCore/jsc.cppSource/JavaScriptCore/parser/Lexer.cppSource/JavaScriptCore/parser/Lexer.hSource/JavaScriptCore/parser/Parser.cppSource/JavaScriptCore/parser/Parser.hSource/JavaScriptCore/parser/SourceProvider.cppSource/JavaScriptCore/parser/SourceProvider.hSource/JavaScriptCore/runtime/CachedTypes.cppSource/JavaScriptCore/runtime/CachedTypes.hSource/JavaScriptCore/runtime/CodeCache.cpp
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- JSTests/stress/line-start-table-not-built-by-ordinary-parse.js
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…very mode The lexer collects a line start in shiftLineTerminator(), so nothing may move over a line terminator in another way. One thing did. While a function body is only checked for syntax, a string is not built, and in a 16-bit source the search for its end did not stop at a character that is not Latin-1. U+2028 and U+2029 are allowed in a string and end a line there, so every line after such a function was one short. That is what the engine did before the upgrade too, when the lexer counted lines. The scan of the text got it right, and so does V8. The search now stops at the two, which takes the slow case, where they are handled. A syntax check of a 16-bit typescript.js executes 600.2 million instructions, and 600.0 before. I went through everything else that moves m_code other than by shift(): identifiers, digits, the value of a comment directive and a single-line comment all stop at a line terminator, and nextTokenIsColon() only looks. line-start-table-positions.js now has each of its constructs in a function, in an arrow function in a function and in a method as well as at the top level. Also, cachedTypesFormatRevision is 12: the last commit made the records of a global code block and of a builtin function's entry larger.
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The two points from the previous run are addressed in HEAD: cachedTypesFormatRevision is now 12, and the UTF-16 DontBuildStrings string fast path stops on U+2028/U+2029 so they reach shiftLineTerminator(). Beyond the inline finding, I also checked the remaining callers of the unguarded LineColumn memo (StackFrame, StackVisitor, DebuggerCallFrame, SamplingProfiler::processUnverifiedStackTraces) — all run on the mutator or under the profiler lock with the mutator stopped, so the cache's no-lock rule holds for them.
Extended reasoning...
Findings-present ruled-out note only: the prior-run issues are fixed in the latest commits, and the non-JIT callers of lineColumnForBytecodeIndex were verified to be mutator-side, leaving the single CodeCache/Function-constructor finding as the open item.
…ompiled, not from the lexer
The lexer collected the line starts while it parsed. That put a duty on it
that upstream took away with the line counting: every line terminator had
to pass through one function, and the parser could not move over text the
lexer had not read. Nothing upstream keeps to that. The search for the end
of a string went over U+2028 and U+2029, the parse of a class field
initializer moves forwards by restoring a lexer state, and any fast path
that upstream adds later could do the same and pass all of its tests.
Lexer.{h,cpp} and Parser.{h,cpp} are what they are upstream again. The
table is made by upstream's scan, at the place where the top-level code
takes it from its source. Loading a module of 1.5 KB to 12 KB in Bun
executes 0.2% to 0.3% more instructions than with the lexer's part, and 2%
to 3% fewer than before the upgrade. The Function constructor and a
builtin with a source of its own, which the lexer covered, have their table
when they are asked for a position, or out of bytecode.
What the lexer needed is gone: the Builder in the header with its two
speeds and its scan of a part, the lists with room in them, the table of
one line, lookups without the lock, the virtual wantsLineStarts().
LineStartTable has upstream's shape again: build(), ensureBuilt() and the
lock, with other storage and a way in and out for the code.
A lookup reads the bytes directly. The first stack trace through a call
site pays for one per frame: with checked spans and WTF::LEBDecoder a
stack trace of 12 frames, all new, executed 20% more instructions than
before the upgrade, and it executes 8% more now.
Also: the comment on why sources can share the kept positions said more
than is true, the layout of the table is part of the bytecode format and
now says so, and CachedLineStarts is in the list of record sizes.
The last commit has only the lexer and the parser put back. This is what its message describes.
…keeps the expression info of builtins
…ce that is parsed The last two commits made the table with a scan of the text when its code was compiled. That is a second pass over every source, which the engine did not do before the upgrade and does not do upstream. A parse of all of a source passes every line of it, so the lexer notes where each starts, in shiftLineTerminator(), and the parser gives the list to the source when the parse has succeeded. That is all that changes in the lexer and the parser. - Only a parse of all of a source collects. A parse of a function or of a class field initializer moves over text that its lexer has not read. - A parse that fails gives nothing. - So there is no scan of what a parse left out. A source without a table is scanned when it is asked for a position, by upstream's code, which is what it was again: a short source, the Function constructor, a builtin with a source of its own that is not run from bytecode, a syntax error. - LineStartTable::build() is upstream's, and encode() makes the table from a list of line starts, the lexer's or build()'s. The search for the end of a string is upstream's too. While a function body is only checked for syntax, in a 16-bit source, it goes over U+2028 and U+2029 in a string without a look, so the lines after such a function are one short, as they were when the lexer counted the lines.
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I reviewed the latest push (the scan-at-compile-time approach in the last two commits) and found no bugs, but because this changes the bytecode cache layout and adds a lock-free position cache in core engine code, a human look is still worthwhile. Note that the PR description still describes the earlier lexer-collected design (and a Lexer.cpp U+2028/U+2029 change) that is no longer in the diff.
What was reviewed:
- Threading of the unguarded
ExpressionInfo::m_cachedLineColumns: the three compiler-thread callers (JIT.cpp, DFGJITCompiler.cpp, FTLCompile.cpp) use the newConcurrentlyvariant; SamplingProfiler's call runs from the Debugger marking constraint inside the Fixpoint phase, which is stop-the-world, so it does not race the mutator. - The InstPC-only cache key: checked that program/eval/module SourceCodes reaching the CodeCache are whole-provider texts, so shared unlinked code has the same text and sourceOffset for every provider.
EncodedLineStartsbuild/walk: block boundaries at 64 lines, the 63-lengths-per-block stream, the empty-text and past-the-end cases, andstartOfLinecallers staying belowlineCount().CachedLineStarts: borrow only undercanBorrowPayload()(persistent payloads, same as strings and ExpressionInfo), revision bump to 12 and the sizeof asserts match the added 8-byte member.
Extended reasoning...
The branch replaces the Vector line-start table in parser/SourceProvider with a LEB128 block encoding, builds it when global code is compiled (CodeCache.cpp) for texts of 1024+ characters, stores it on UnlinkedGlobalCodeBlock and in the bytecode cache (CachedTypes.cpp, format revision 12), adds a per-InstPC LineColumn memo in ExpressionInfo, and gives builtins a provider that counts positions from each builtin's start. It touches no injection, auth or data-exposure surface, but the raw-pointer decoder and the mapped-payload borrowing are memory-safety-sensitive. Deferring rather than approving because the change is large (27 files, +552/-159) and design-heavy, the PR description no longer matches the implementation after the last two commits, and the correctness of the lock-free memo rests on threading assumptions a maintainer should confirm for Bun's own callers outside this repo. No outstanding third-party objection is visible: all coderabbit threads were resolved by the author with follow-up commits.
This review covers commit 9e20a36, which is no longer the latest commit on this pull request; later commits are not covered by it.
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Only a parse of all of a source leaves its line starts behind, so the Function constructor and a module of Bun's own that is not run from bytecode have their table when they are asked for a position. A build with assertions keeps the positions in builtins, so its frame in Array.prototype.map is the call in it, not where the builtin starts.
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Fixes #25559
Upgrades the WebKit fork to upstream WebKit `7b485a76e9` (2026-09-23):
970 upstream commits since the previous merge base `ccdcb8a026`, about
200 of them in JavaScriptCore, WTF, bmalloc or cmake. Fork PR:
oven-sh/WebKit#725. This PR replaces #42666 (upstream `6b58d86abe`, the
first 216 commits of the range) and contains its source edits.
### Pin
- `WEBKIT_VERSION` is `f20ce77445`, the fork's main. It holds
oven-sh/WebKit#725 (the upgrade) and oven-sh/WebKit#734 (positions).
- oven-sh/WebKit#725 landed as a squash. The tree of `74650443cb` is
identical to the tree of `3a8b1bc93b`, the head that CI tested here
before. The squash has no upstream parent, so `git merge-base` with
upstream is still `ccdcb8a026`. The next upgrade must name `7b485a76e9`
as its base by hand, unless someone first records the merge on the
fork's main (`git merge -s ours` of the branch
`bun/upgrade-to-7b485a76e9`).
### Problem
- The fork is 970 commits behind upstream. #42666 stopped at
`6b58d86abe` and did not land.
- #25559: a `++array.length` loop is quadratic past 100000 elements.
Upstream `ab1caf1170` fixes `JSArray::setLength`. The loop of the issue
takes 5152 ms on the current release build and 726 ms on the debug +
ASAN build of this PR.
### Fix
- `WEBKIT_VERSION` points at the fork's main, with oven-sh/WebKit#725
and oven-sh/WebKit#734.
- `error.stack` costs what it did before the upgrade, within a few
percent (see Downsides). With offsets only, upstream reads a whole
source the first time a position in it is asked for, and decodes the
expression info again for every position. In oven-sh/WebKit#734 the
lexer notes where the lines start while it parses a whole source, the
code and its bytecode carry that table, and each position that was
looked up is kept. Nothing of that is in Bun.
- Upstream no longer stores lines and columns (`c76c52f5b1`).
`SourceCode(provider, firstLine, startColumn)` is gone, and 3 of Bun's 5
call sites would still compile with the integers read as source offsets.
All 5 now pass offsets only, and the provider's start position carries
the node:vm `lineOffset` and `columnOffset`.
- The other source edits follow upstream API changes:
`Error.stackTraceLimit` storage, `CheckedPtr` plumbing for inspector
agents, typed C strings, `ASCIICString` heap names, `char8_t` option
strings. "Notes for Bun" lists each one.
- The builtins share one text, and a `SourceCode` no longer has a first
line, so `at map (native:1:11)` had become `at map (native:3323:11)`.
The source of Bun's builtins, like that of JavaScriptCore's, is now a
`BuiltinsSourceProvider`, which is told where each builtin starts and
counts from there. `processTicksAndRejections (native:7:39)` and the
rest are what they were.
- Verified: `test/js/bun/jsc/webkit-upgrade-7b485a76e9.test.ts` (22
cases, 10 fail on main), 5 cases in `bun-build-compile.test.ts` for the
sources of an executable (fail without oven-sh/WebKit#734), 4
`Error.appendStackTrace` cases in `capture-stack-trace.test.js` (3 fail
on main) and a `SourceTextModule` position case in `vm.test.ts` (fails
on main). `test/bundler/bundler_bytecode_portable.test.ts` has a new
snapshot, because the bytecode cache format changed. 80 outputs with
positions in them are the same as on main: 20 sources, each run from a
file and compiled three ways. The Notes list the other suites.
### Background
- JavaScriptCore used to store a line and a column next to every source
offset in the parser, in `ExpressionInfo` and in the bytecode cache. It
now stores offsets only. `SourceProvider` builds a table of line starts
the first time someone asks for a line or a column, for example when
`Error.stack` is read.
- The bytecode cache (`bun build --bytecode`, `--compile`) has no line
and column fields any more. Payloads in the portability test are 3% to
6% smaller. The cache version is a hash of `WEBKIT_VERSION`, so a new
build rejects old payloads and compiles from source.
- `Error.stackTraceLimit`: JSC kept the limit in a C++ field that only a
`put` on the constructor updated. It now reads the own property of the
`Error` constructor when it captures a stack, as V8 does. Bun's default
of 10 moves to `Options::defaultErrorStackTraceLimit()`.
### Downsides
- Behaviour changes that code could depend on:
`vm.runInNewContext("Error.stackTraceLimit")` is 10 (was 100, Node gives
10). `TypeError.stackTraceLimit = n` and a setter installed on
`Error.stackTraceLimit` no longer change the limit. `BigInt("-")`,
`BigInt("+")` and `BigInt("0x ")` throw `SyntaxError` (were `0n`).
`Intl.DurationFormat("en", { hours: "numeric" }).format({ hours: 1 })`
is `"1:00:00"` (was `"1"`). `Intl.DateTimeFormat`
`resolvedOptions().dayPeriod` is `undefined` for an AM/PM pattern (was
`"short"`). `resize(-1)` and `resize(2 ** 53)` on a detached
`ArrayBuffer` throw `RangeError` (were `TypeError`, and Node throws
`TypeError`): the specification runs `ToIndex` before the detached check
(`223bd0faee`). Of 26 behaviours compared with Node 26.3, 12 changed to
Node's result and this one changed away from it.
- A position now takes a lookup in the source's table of line starts,
which the code did not need when it had its lines and columns. A stack
trace whose call sites are all new executes 3% (1 function deep) to 6%
(10 deep) more instructions than on main. The first `error.stack` in a
file takes 4 to 5 µs longer (20 µs against 15 µs at 100 KB, 27 µs
against 23 µs at 10 MB), where upstream alone takes 2.5 ms at 10 MB.
Repeated reads are 0.95 to 1.05 of main over 22 cases. In a 100 MB
module compiled with `--bytecode` the first read takes 0.03 ms and 0.6
MB of RSS, where upstream alone takes 34.5 ms and 137 MB. Loading a
module of 500 to 12,000 characters executes 2.7% to 3.6% fewer
instructions than on main. The tables are in oven-sh/WebKit#734.
- Positions that change, found by running 37 constructs through
`node:vm` and about 120 scripts of every feature that reports a position
(call sites, uncaught errors, `bun test` output, junit, inline
snapshots, coverage, `--cpu-prof`, the inspector) on main and on this
branch. Everything else was the same.
- The `new X` frame under a field initializer that throws is where the
constructor's parameters start: `4:14` (was `4:15` to `4:17`). Node
gives `4:14`.
- A position in a class field initializer on the same line as the
enclosing function has its true column: `1:45`, and `1:67` with 22
characters before it (was `1:35` for both). That is the shape of
minified code.
- `vm.SourceTextModule` applies `lineOffset` and `columnOffset` as Node
does (both were one short).
- A runtime error in a `vm.Script` with a negative `lineOffset` prints
the source line and a caret, as Node does.
- The frame that disposes a `using` is where its scope ends, `6:2` (was
the first line of the function with a column that meant nothing,
`2:12`). Node gives the last statement, `5:4`.
- The frame of an implicit base-class constructor is `unknown:1:11` (was
`unknown:1:17`). Both are positions in a text that the engine makes up.
- Bytecode holds the line starts of its source, about one byte per line.
It is still smaller than before the upgrade, because it shrank by more
(what TypeScript's `tsc` embeds with `--bytecode`: 16.49 MB to 16.17
MB). An executable without bytecode embeds what it did.
- Upstream's `WeakBlock` redesign (`7f5ab15882`, one week old upstream)
makes `WeakImpl::clear()` edit the free list and the counts of a block
without a lock. A `JSC::Weak` that is destroyed by a thread without the
API lock, or by the lock owner while it has released heap access, now
corrupts the weak blocks. I found no such call: 174,668 probed calls,
and about 4,700 tests with an assertion in `WeakBlock::deallocate`,
child processes included. Not covered: macOS, Windows, native addons
that delete a reference on their own thread, and code that no test runs.
<details><summary>Notes for Bun: every source edit, and what was
verified</summary>
New in this PR (upstream `6b58d86abe..7b485a76e9`):
- `SourceCode` (`c76c52f5b1`). `src/codegen/bundle-functions.ts`,
`JSCommonJSModule.cpp`, `NodeVM.cpp` (two sites) and
`NodeVMSourceTextModule.cpp` drop the line and column arguments. The
three-argument sites in `NodeVM.cpp` and `NodeVMSourceTextModule.cpp`
are the ones that would have compiled with the integers read as
`startOffset` and `endOffset`.
- node:vm start positions. JSC now adds the provider's start position to
every derived line and column, as unsigned numbers. The old `SourceCode`
constructor clamped `firstLine` and `startColumn` to 1. With
`lineOffset: -5`, the unclamped provider gave `e.line === 4294967293`
and broke the arrow header of compile-time errors (2 cases of
`vm.test.ts`). The new `providerStartPosition()` in `NodeVM.cpp` clamps
at zero for `vm.Script`, `vm.compileFunction` and `vm.SourceTextModule`.
`decorateParseErrorStack()` keeps its logic that applies the sign again.
Result: the same output as before this PR for negative offsets. Not
changed by this PR: `vm.compileFunction` reports the first body line one
too high for `lineOffset` 0 and 1 (`vm.js:2`, where Node prints
`vm.js:1` and `vm.js:2`). The 1.4.3 release prints the same lines as
this branch for offsets 0, 1, 5 and -3, and #38240 is the open PR for
it.
- `vm.SourceTextModule` passed zero-based numbers to the one-based
`SourceCode` arguments. With the provider as the only source of the
start position, a module with `lineOffset: n` now reports the same lines
as `vm.Script` with `lineOffset: n`, which is also what Node reports.
`vm.test.ts` has a case for it. #38235 covers the rest of the module
offsets (negative values, the identifier as the file name).
- `Error.appendStackTrace` (fork commit `eacf0ea760`). The fork's
`ErrorInstance::captureStackTrace()` called `value()` on
`JSGlobalObject::stackTraceLimit()`. The limit is empty for a value that
is not a number and for a deleted property, and since `a5bfdb3aaf` also
for `NaN` and for an accessor. `Error.stackTraceLimit = NaN;
Error.appendStackTrace(new Error("a"), new Error("b"))` aborted the
process. The string and the deleted form abort on main too. It now
captures zero frames, like `Error.captureStackTrace`.
- `ErrorStackFrame.cpp`: `ExpressionInfo::Entry` has no `lineColumn`.
`getAdjustedPositionForBytecode()` asks
`SourceProvider::documentLineColumnForOffset()` for the divot.
- `NodeVM.cpp` `decorateParseErrorStack()`: `JSTextPosition::column()`
is gone. The caret column is the distance from the token offset back to
the previous `\n` of the source, which is also how
`nthSourceLineForArrowHeader()` splits lines.
- `Error.stackTraceLimit` (`a5bfdb3aaf`):
`JSGlobalObject::setStackTraceLimit()` is gone. `JSCInitialize` sets
`Options::defaultErrorStackTraceLimit()` to 10. Every realm's `Error`
constructor starts from that option, so node:vm contexts now start at 10
(they started at 100, Node gives 10). `ShadowRealm` already had 10.
- Inspector agents (`9a8a5f7d36`): `InspectorAgentBase` derives from
`AbstractCanMakeCheckedPtr`. `InspectorLifecycleAgent`,
`InspectorTestReporterAgent`, `InspectorHTTPServerAgent` and
`InspectorBunFrontendDevServerAgent` add `CanMakeThreadSafeCheckedPtr`,
`WTF_OVERRIDE_DELETE_FOR_CHECKED_PTR` and
`OVERRIDE_ABSTRACT_CAN_MAKE_CHECKEDPTR`. The thread-safe base is what
upstream uses for agents whose controller can be destroyed on another
thread.
- `BunGCOutputConstraint.cpp`, `BunClientData.cpp` (`9b5592466b`):
marking constraint names are `ASCIICString`, so the literals take `_s`.
- `BunJSCModule.h` (`58e02c19b9`): `Options::samplingProfilerPath()` is
a `const char8_t*`, so the store takes `pathCString.data()`. The edit
adapts the type and nothing else: the statement segfaults on every call,
on main too, because the options are read-only after `Config::finalize`
(#32212), and #41137 replaces it.
- `JSSecrets.cpp` (`29a96fa550`): `CString::mutableSpan()` is protected.
`SecretsJobOptions` holds `UTF8CString`, which keeps `mutableSpan()`
public, so the destructor still zeroes the buffers. The platform
functions keep their `const CString&` parameters.
- `bindings.cpp` (`c17d3df6ec`): includes
`wtf/PlainGregorianDateTime.h`.
- `bundler_bytecode_portable.test.ts`: every hash moves, as the file's
header says for a format change. The bundled JS hashes do not move.
From #42666 (upstream `ccdcb8a026..6b58d86abe`):
- `String::utf8()` returns `UTF8CString` (`00130dc2f3`), whose `data()`
is a `const char8_t*`. 48 calls in 17 files give a NUL-terminated string
to a C function or to a format string, and they call
`legacyCStringPointer()`. The class generator emits the same pattern. 13
calls pass bytes and a length, and they use `span()`.
- `toCString()` is `toUTF8CString()` (`7189f73167`). `WeakGCMap` holds
raw pointers (`8ae0649a80`, `SecureContextCache::set()`).
`String(std::span<const char>)` is private (`74b519d7f9`,
`BunProcess.cpp`). `dataLog()` has no `const char8_t*` overload
(`BunAnalyzeTranspiledModule.cpp`).
- `scripts/verify-baseline-static/allowlist-x64-windows.txt`: this PR no
longer changes it. Its entry `__std_max_8i` was for `5e03b0c541`, which
uses `std::max` over an initializer list of `int64_t` (the MSVC STL
vectorizes that behind an `__isa_available` test). Main now lists the
code of the MSVC STL as `<lib:libcpmt.lib>` (#43704), and the merge of
main (`efdc463da7`) took that entry.
- Tests of #42666. The 5 cases of its
`webkit-upgrade-6b58d86abe.test.ts` are in
`webkit-upgrade-7b485a76e9.test.ts`, some in a longer form (the BigInt
case has its 8 operand shapes plus 6). Its
`webkit-upgrade-ccdcb8a026.test.ts` is carried over as a file: 5 cases
for the previous upstream range, which pass before and after this
upgrade.
Review of this diff (what I checked by hand, and how):
- Stack position of a class field initializer: **a regression, repaired
in the fork.** For a base class with an explicit constructor, `endpoint
= config.url` with `config === null` gave `at new Client (file.ts:7:15)`
on main (the `constructor(` line) and `at new Client (file.ts:9:21)`
with the pin `eacf0ea7` (the last statement of the constructor). Bun's
code frame then puts the caret on a line that did not throw. Cause:
upstream `c76c52f5b1`. The old `StatementNode::setLoc()` gave a scope
node the first line of the function next to the offset of its end, and a
frame used the line. Fork commit `3a8b1bc93b` gives the call the offset
where the constructor starts: `at new Client (file.ts:7:14)`, which is
what Node 26.3 prints. Upstream `main` still has the old call. The
expression info stores that offset, so the bytecode snapshot changes for
the 16 payloads that have a class with instance fields, and the 11
without one keep their hash.
- `using` and `await using`: the frame of the function that owns the
declaration moved from its first line to the statement that leaves the
scope (`work (2:14)` to `work (6:10)`). Node prints `work (6:12)`, so
this stays.
- `SourceCode` call sites: a scan of `src/` for every `SourceCode(...)`
finds 29 calls with one argument and 2 with three,
`bundle-functions.ts:468` and `JSCommonJSModule.cpp:176`. Both pass
`startOffset` and `endOffset`. No call passes a line and a column.
- `ErrorStackFrame.cpp`: `CodeBlock::expressionInfoForBytecodeIndex()`
adds `sourceOffset()` to the divot, so the divot that
`getAdjustedPositionForBytecode()` gives to
`documentLineColumnForOffset()` is an offset in the provider. Upstream's
`CodeBlock::lineColumnForBytecodeIndex()` does the same.
- `allowlist-x64.txt`: in a release build with LTO and the baseline
features, the region that the scanner counts as
`ipint_op_memory_atomic_wait64` is 43,831 bytes and has 8 AVX
instructions. They are the same sequences as in the handlers of
`v128.load8_splat`, `load16_splat`, `load32_splat` and `load64_splat` (3
+ 3 + 1 + 1). The gate is `Options.cpp:943`: `if (isX86_64() &&
!isX86_64_AVX()) Options::useWasmSIMD() = false`.
- `JSSecrets.cpp`: `mutableSpan()` copies a buffer that is shared, so
the destructor would then zero a copy. A breakpoint on
`~SecretsJobOptions()` shows a reference count of 1 for `password`,
`name` and `service` in `set`, `get` and `delete`, so the zeroing is in
place. The container has no keyring, so each call ended with
`ERR_SECRETS_PLATFORM_ERROR`.
- `FuzzilliREPRL.cpp`: no CI lane builds with `FUZZILLI_ENABLED`.
Compiled by hand with that flag, the file of this PR compiles, links and
runs. The file of main does not compile against the new WebKit (`format
specifies type 'char *' but the argument has type 'const char8_t *'`).
- Three worker test files fail on my machine and pass in CI.
`worker.test.ts` and `worker-late-completion.test.ts` hit the 5 second
limit on a host with a load average of 110 (CI, `x64-asan`: 42 of 42 in
3.5 s and 33 of 33 in 7.7 s). The `dns.lookup()` case of
`worker-terminate-lifetime.test.ts` is a LeakSanitizer report at
`node_fs_binding.rs:183` (#39684), in a container without DNS.
Measurements (Linux x64, release builds with LTO of main `8d36bff512`
and of this PR at `701805bae0`, runs interleaved A/B, host load average
about 110, so the quartiles are beside each median):
| | main q1 / median / q3 | this PR q1 / median / q3 |
|---|---|---|
| First `.stack` read, 10 MB source with 90,177 functions (15 runs) |
0.034 / 0.036 / 0.038 ms | 7.31 / 7.63 / 7.79 ms |
| Next 1,000 `.stack` reads, same source | 2.40 / 2.49 / 2.70 ms | 2.72
/ 2.82 / 2.91 ms |
| User CPU of that process | 662 / 684 / 699 ms | 647 / 649 / 665 ms |
| Peak RSS of that process | 105.9 / 106.9 / 107.1 MB | 102.5 / 103.5 /
104.6 MB |
| `new Error().stack`, 2 frames (9 runs) | 2.82 / 3.00 / 3.07 µs | 2.34
/ 3.41 / 3.57 µs |
| `new Error().stack`, 10 frames | 9.04 / 10.04 / 10.53 µs | 9.36 /
11.70 / 12.04 µs |
| `new Error().stack`, 50 frames | 38.2 / 43.3 / 43.7 µs | 39.2 / 46.9 /
49.3 µs |
| `new Error()`, 10 frames, no read of `.stack` | 0.45 / 0.63 / 0.68 µs
| 0.43 / 0.69 / 0.70 µs |
| Startup, `console.log` only, user CPU (25 runs) | 1.95 / 3.02 / 4.05
ms | 1.92 / 2.95 / 3.73 ms |
| Text section of the binary (`size`) | 80,675,832 bytes | 80,452,686
bytes |
The quartiles of the `new Error().stack` rows overlap. The medians are
higher on this PR at every depth (1.14, 1.09, 1.17 and 1.08 times), so
the slowdown is probably real and about 10%. `perf`, `valgrind` and
`strace` are not installed on the machine, so there are no instruction
counts.
`WeakImpl::clear()` and threads. A `Weak` may be destroyed by the thread
that holds the API lock while it has heap access, or by a GC thread
while the world is stopped. `WeakSet::allocate()` asserts the lock, and
nothing asserts it on deallocation. Bun releases heap access in one
place: `us_loop_run_bun_tick` (`epoll_kqueue.c`), between
`Bun__JSC_onBeforeWait` and `Bun__JSC_acquireHeapAccessAfterWait`, when
an idle collection is pending (#43681). In that window the thread runs
the poll and the mimalloc idle hooks. The libuv loop never releases
access.
Measured on Linux x64 with the debug build, with
`BUN_IDLE_GC_SECONDS=1,1,1`:
- A gdb breakpoint on `WeakImpl::clear()` that reads the owner of the
`JSLock`, the `hasAccessBit` of `Heap::m_worldState` and
`Heap::m_worldIsStopped`. 15 runs (12 worker, `MessagePort` and
`BroadcastChannel` test files, `napi.test.ts`, the upgrade test and a
workload with 3 workers, transfers, `fs` and `fetch`): 174,668 calls and
99 parks without heap access. 172,647 calls came from the lock owner
with heap access. 2,021 came from the collector thread with the world
stopped and the JS thread parked, all from `Heap::sweepArrayBuffers()`.
None came from the lock owner without access or from another thread.
- An assertion in `WeakBlock::deallocate` (not in this PR). Two controls
show that it fires: a call from a `Bun Pool` thread gives `ASSERTION
FAILED: m_heap.vm().currentThreadIsHoldingAPILock()`, and a call from a
JS thread that is parked without access gives `ASSERTION FAILED:
m_heap.hasHeapAccess()`. With that build, `test/js/web/workers`,
`test/js/node/worker_threads`, `test/js/web/broadcastchannel`,
`test/napi` and `test/js/web/abort` ran in full, and
`test/js/web/fetch`, `test/js/bun/http` and `test/js/web/streams` ran
for 12 minutes each: about 4,700 passing tests, child processes
included, no assertion failure.
- `napi_delete_reference` in a finalizer stays safe: `WeakSet::sweep`
keeps the block it walks linked (`WeakBlock::IterationScope`) and reads
the next block after the finalizers ran. This PR removes the stale
sentence from the comment there.
- The debug + ASAN `jsc` shell of this WebKit fails
`JSON-parse-reviver.js`: `JSONObject.cpp` and `CloneBase.h` both define
`JSC::WalkerState`, with 4 bytes and 1 byte, and `jsc.cpp` now uses
both. Bun does not have the problem: no file of Bun or of the
JavaScriptCore library includes the clone headers, and the test passes
in Bun (debug + ASAN and release). The fix for the shell is
oven-sh/WebKit#733.
`apply` and `arguments.length` (`a0e2a50e76`): upstream fixed
`sizeOfVarargs()` for a strict `arguments` object only. A sloppy one
with `length = 2 ** 32 + 1` still wraps to 1, before and after this PR
(Node throws `RangeError`). In a CommonJS file Bun drops a
function-level `"use strict"` (#40838), so the function of upstream's
example has a sloppy `arguments` object there.
Checked and unchanged: `runtime/JSType.h`, the fork's
`.github/workflows`, the release tarball names. The WebCore bindings
generator changes do not touch code that Bun's bindings use. JSC
options: `weakBlockPoolDivisor` (16) and `useB3SpecializeSelect` (true)
are new, none is removed.
Verified on Linux x64 with `bun run build:local` (Bun debug + ASAN
against the fork branch at `3a8b1bc93b`): `bun-debug -p 42` prints 42.
These files pass: `webkit-upgrade-7b485a76e9.test.ts` (18),
`webkit-upgrade-ccdcb8a026.test.ts` (5) and the five older
`webkit-upgrade-*.test.ts` files, `node/vm/vm.test.ts`, `vm-sourceUrl`,
`script-leak`, `sourcetextmodule-leak`, `sourcetextmodule-link-gc`,
`vm-script-fetcher-leak`, `happy-dom-vm-16277`,
`node/v8/capture-stack-trace.test.js` (68),
`bun/util/inspect-error.test.js` (39), `inspect.test.js`, `reportError`,
`error-gc-test`, `bun/test/stack.test.ts`, the inline snapshot tests,
`expect-stack-overflow-crash`, `cli/test/coverage.test.ts` (14),
`cli/inspect/` (`inspect`, `bun-inspector-protocol`, `HTTPServerAgent`,
`test-reporter`, `BunFrontendDevServer`, `compile-bytecode-tooling`),
`bun/jsc/bun-jsc.test.ts` (41),
`bun/sourcemap/internal-sourcemap.test.ts`, `bun/cookie/cookie.test.ts`,
`web/workers/worker.test.ts` (42),
`node-inspect-tests/parallel/util-inspect.test.js`, and
`bundler_bytecode_portable.test.ts` (22, with the new snapshot).
`web/fetch/fetch.test.ts` has 6 failures and `bun/http/serve.test.ts`
has 2. The same 8 fail with the release build of main in my container:
it runs as root and has no IPv6.
Not compiled locally: the Windows and macOS code paths. I read every
platform-specific use of `CString`, `utf8()`, `SourceCode` and the other
changed APIs in `src/`. CI builds them for real.
</details>
<details><summary>Upstream changes, 6b58d86abe..7b485a76e9 (754 commits,
154 touch JavaScriptCore, WTF, bmalloc or cmake)</summary>
Each commit appears once, under the most specific heading that applies.
### Needs an embedder-side change, or a check
- `c76c52f5b1` The parser and the bytecode keep source offsets only.
`SourceProvider` derives lines and columns from a lazy `LineStartTable`.
`SourceCode` loses `SourceCode(Ref<SourceProvider>&&, int firstLine, int
startColumn)` and the last two arguments of the five-argument form. An
old three-argument call still compiles, with its integers read as
`startOffset` and `endOffset`. Write `SourceCode(WTF::move(provider))`.
The start position of the provider now carries the line and column
offset. `JSTextPosition` keeps only `offset` and loses `line`,
`lineStartOffset` and `column()`. `ExpressionInfo::Entry::lineColumn`,
`UnlinkedCodeBlock::lineColumnForBytecodeIndex()` and
`CodeBlock::firstLineColumnOffset()` no longer exist. Call
`CodeBlock::lineColumnForBytecodeIndex()`,
`SourceProvider::positionInfoForOffset()` or
`SourceProvider::documentLineColumnForOffset()`.
`SourceCode::firstLine()` and `startColumn()` now build the line table.
`SourceCode::subExpression()`, `ScriptExecutable::recordParse()`,
`parseRootNode()` and `parseFunctionForFunctionConstructor()` lose their
line and column parameters. `Lexer<T>::isWhiteSpace()`,
`isLineTerminator()`, `convertHex()` and `convertUnicode()` become free
functions in `parser/SourceCharacters.h`. The bytecode cache layout is
not compatible: `CachedTypes.cpp` and the `ExpressionInfo` encoding drop
all line and column fields. A raw U+2028 or U+2029 inside a string
literal now starts a new line for reported line numbers.
https://bugs.webkit.org/show_bug.cgi?id=324564
- `a5bfdb3aaf` `JSGlobalObject::setStackTraceLimit()` and
`m_stackTraceLimit` no longer exist. `JSGlobalObject::stackTraceLimit()`
reads the own data property `stackTraceLimit` of the realm `Error`
constructor with `getDirect()`. It returns `std::nullopt` for a value
that is not a number. The initial `Error.stackTraceLimit` comes from
`Options::defaultErrorStackTraceLimit()` (default 100).
`Object.defineProperty(Error, "stackTraceLimit", { value: 3 })` and
inline-cached `Error.stackTraceLimit = n` writes now change the limit.
`TypeError.stackTraceLimit = 2` and a setter installed on
`Error.stackTraceLimit` no longer change it, which matches V8. The
commit message states a cost of about 3 ns per `new Error()`.
https://bugs.webkit.org/show_bug.cgi?id=324314
- `9a8a5f7d36` `Inspector::InspectorAgentBase` now derives from
`WTF::AbstractCanMakeCheckedPtr`. Each concrete agent must add a
`CanMakeCheckedPtr<T>` or `CanMakeThreadSafeCheckedPtr<T>` base,
`WTF_OVERRIDE_DELETE_FOR_CHECKED_PTR(T)` and a public
`OVERRIDE_ABSTRACT_CAN_MAKE_CHECKEDPTR(...)`. Upstream uses the
thread-safe base where teardown can run on another thread.
`JSGlobalObjectInspectorController` now holds agents as `CheckedPtr`
members and declares `m_agents` before them. `m_consoleClient` is now
`const`, so a constructor must call `lazyInitialize(m_consoleClient,
...)`. https://bugs.webkit.org/show_bug.cgi?id=324216
- `9b5592466b` JSC heap names change type from `CString` to
`ASCIICString`. This applies to the constructors of `Subspace`,
`IsoSubspace`, `CompleteSubspace`, `PreciseSubspace`,
`MarkingConstraint`, `SimpleMarkingConstraint`, `SlotVisitor` and
`AbstractSlotVisitor`, and to `MarkingConstraintSet::add()`.
`ASCIICString` has an implicit constructor from `ASCIILiteral`, but its
`const char*` constructor is `explicit`. A caller that passes a plain
literal must add `_s`. `Subspace::name()`, `MarkingConstraint::name()`,
`abbreviatedName()` and `AbstractSlotVisitor::codeName()` now return
`const ASCIICString&`. `ProfilerSupport::markStart()`, `markEnd()`,
`mark()` and `markInterval()` now take `UTF8CString&&`.
`StringPrintStream::toASCIICString()` and `WTF::toASCIICString()` are
new. https://bugs.webkit.org/show_bug.cgi?id=324651
- `58e02c19b9` `OptionsStorage::OptionString` in `runtime/OptionsList.h`
changes from `const char*` to `const char8_t*`. All string option
accessors, for example `Options::samplingProfilerPath()`, now have that
type. The option stores the raw pointer and does not copy the string.
`SourceProvider::sourceCodeDumpFilePath()` takes and returns
`UTF8CString`. WTF adds `String(const char8_t*)` and
`printInternal(PrintStream&, const char8_t*)`. Four sites that decoded
option paths as Latin-1 now decode them as UTF-8.
https://bugs.webkit.org/show_bug.cgi?id=324652
- `c17d3df6ec` `WTF::GregorianDateTime` and `wtf/GregorianDateTime.h` no
longer exist. `PlainGregorianDateTime` moves from
`JavaScriptCore/PlainGregorianDateTime.h` (namespace `JSC`) to
`wtf/PlainGregorianDateTime.h` (namespace `WTF`, with a global `using`).
`PlainGregorianDateTime::fromMilliseconds(double)` and
`currentLocalTime()` replace the old constructor and
`setToCurrentLocalTime()`. The class is a 64-bit payload without
setters, `yearDay()`, `operator tm()` or the `offsetOf...()` functions.
`DateCache::msToGregorianDateTime()`,
`DateInstance::gregorianDateTime()` and `formatDateTime()` already used
`PlainGregorianDateTime`. https://bugs.webkit.org/show_bug.cgi?id=324677
- `29a96fa550` `CString(ASCIILiteral)`, `CString(CStringBuffer*)`,
`CString::mutableSpan()`, `mutableSpanIncludingNullTerminator()` and
`grow()` are now `protected`. `CString(const std::string&)` no longer
exists. `UTF8CString`, `Latin1CString` and `ASCIICString` keep
`mutableSpan()`, `grow()` and the `ASCIILiteral` constructor public.
`safePrintfType(const Latin1CString&)` is deleted.
`JIT::compileTimeStats()` returns `UncheckedKeyHashMap<ASCIICString,
Seconds>`. https://bugs.webkit.org/show_bug.cgi?id=324791
- `99452a3d81` `CString::newUninitialized()` becomes `protected`. Call
`ASCIICString::newUninitialized()`, `UTF8CString::newUninitialized()` or
`Latin1CString::newUninitialized()`. `WTF::setCrashLogMessage()` (Cocoa)
now takes `UTF8CString&&`. `wtf/Forward.h` now exports `ASCIICString`,
`UTF8CString`, `Latin1CString` and `CStringWithEncoding` to the global
namespace. https://bugs.webkit.org/show_bug.cgi?id=324692
- `fd27a24dd1` `StringTypeAdapter<CString>` has a deleted constructor.
`makeString()` and `StringBuilder::append()` reject an untyped `CString`
at compile time. Keep the typed value (`auto s = string.utf8()`), or
pass a span. `TextStream` declares `operator<<(const CString&)` as `=
delete`. `WTF::safeStrerror()` returns `UTF8CString`, and its `length()`
is now the message length.
https://bugs.webkit.org/show_bug.cgi?id=324230
- `eefa5dc4c3` `CString` loses `CString(std::span<const
Latin1Character>)` and `CString(std::span<const char8_t>)`. For bytes
with no known encoding, write `CString(byteCast<char>(bytes))`. For
text, use a typed constructor such as `UTF8CString {
byteCast<char8_t>(bytes) }`. `URLHelpers::userVisibleURL()` now takes
`std::span<const char8_t>`. `TextStream` gains `operator<<` overloads
for the typed strings. https://bugs.webkit.org/show_bug.cgi?id=324082
- `7e37c8055a` `WTF::toHexCString()`, `SHA1::hexDigest()` and
`SHA1::computeHexDigest()` return `ASCIICString`.
`CStringWithEncoding::legacyCStringPointer()` now exists only for
`UTF8CString`. On an `ASCIICString`, call `data()`.
`Wasm::NameSection::setHash()` takes `const
std::optional<ASCIICString>&`.
https://bugs.webkit.org/show_bug.cgi?id=324076
- `8217890851` `SHA1::addBytes(const CString&)` and
`Persistence::Coder<CString>` no longer exist.
`base64EncodeToStringReturnNullIfOverflow(const CString&, ...)` now
takes `const Latin1CString&`.
https://bugs.webkit.org/show_bug.cgi?id=324322
- `f5430ef75d` Intl code carries locale identifiers as `ASCIICString`.
`canonicalizeUnicodeLocaleID()`,
`localeIDBufferForLanguageTagWithNullTerminator()`,
`IntlCache::getBestDateTimePattern()` and
`IntlCache::getFieldDisplayName()` take `const ASCIICString&`. WTF adds
`StringView::ascii()` and `StringImpl::asciiForCharacters()`.
`IntlCache::canonicalizeUnicodeLocaleID()` returns a null `String` for a
non-ASCII tag without an ICU call.
https://bugs.webkit.org/show_bug.cgi?id=324324
- `7f5ab15882` `WeakBlock` now counts its allocated, live and dead
`WeakImpl` slots, so `Heap` no longer scans logically-empty blocks.
`Heap` pools empty blocks for all `WeakSet`s, and block stealing no
longer skips a `MarkedBlock` that had `WeakBlock`s. The new option
`weakBlockPoolDivisor` (default 16) keeps one pooled block per 16
`MarkedBlock`s. `WeakImpl::clear()` moves to `WeakBlock.h`. It now
updates the free list and the counters of the block without a lock, and
it can release the block. The old `clear()` only wrote a tag.
`Heap::addLogicallyEmptyWeakBlock()`, `WeakBlock::SweepResult`,
`takeSweepResult()`, `isLogicallyEmptyButNotFree()` and
`disconnectContainer()` no longer exist. New: `Heap::weakBlockCount()`,
`$vm.weakBlockCount()`, and `alignedMalloc()` plus `tryAlignedMalloc()`
on `FastMalloc` and `FastCompactMalloc`.
https://bugs.webkit.org/show_bug.cgi?id=324140
- `7692eececb` `WeakGCSet<T>` stores raw `T*` values, like `WeakGCMap`
since `8ae0649a80`. `reconcileWeakReferencesAtGCEnd()` removes unmarked
entries in eden and full collections. Iteration yields `T*`, and each
entry is live. `WeakGCSetHash` and `WeakGCSetHashTraits` no longer
exist. `JSGlobalObject::WeakCustomGetterOrSetterHash<T>::hash()` and
`equal()` take `T*`. `WeakGCSet.h` and `WeakGCSetInlines.h` no longer
include `WeakInlines.h`. https://bugs.webkit.org/show_bug.cgi?id=324122
- `aa19dc61a0` The last parameter of the `IsoSubspace` constructor
changes from `std::unique_ptr<AlignedMemoryAllocator>&&` to
`AlignedMemoryAllocator*`, with default `nullptr`. `ISO_SUBSPACE_INIT`
needs no edit. All `IsoSubspace` objects now share
`Heap::fastMallocAllocator`, and structure subspaces share the new
`Heap::structureAllocator`. A `LocalAllocator` can thus steal an empty
`MarkedBlock` from any subspace on the same allocator. The option
`stealEmptyBlocksFromOtherAllocators` (default `true`) still controls
this. `AlignedMemoryAllocator::registerDirectory()`,
`registerSubspace()`, `firstDirectory()` and
`Subspace::findEmptyBlockToSteal()` no longer exist. This is the second
landing of `fe81aba198`, which upstream reverted in the previous range.
https://bugs.webkit.org/show_bug.cgi?id=324020
- `d2cffa902f` JSC's `CloneSerializerBase` and `CloneDeserializerBase`
now handle `ArrayBuffer`, `SharedArrayBuffer`, typed arrays, `DataView`,
`WebAssembly.Module` and shared `WebAssembly.Memory`. The
`CloneDeserializerBase` constructor has a new fourth parameter of type
`CloneDeserializationSideChannels`. `CloneSerializerBase` gets a second
template parameter `SideChannelsType`.
`ArrayBufferContents::shareWith()` and its `operator bool()` become
`const`. Bun's `SerializedScriptValue.cpp` has its own serializer and
does not use these classes.
https://bugs.webkit.org/show_bug.cgi?id=324104
### Runtime, parser and builtins
- `7b485a76e9` The bytecode compiler emits a guarded
`op_construct_varargs` for `Reflect.construct(target, args[,
newTarget])` call sites. The guard makes the ordinary call when the
callee is not the original `Reflect.construct` or the arguments fail its
validation. Microbenchmarks are 1.42x to 3.43x faster. On the fast path,
`Error.stack` has no native `construct` frame between the constructor
and the caller. The new `LinkTimeConstant::reflectConstructFunction`
shifts the values of later `LinkTimeConstant` entries, which cached
bytecode stores. https://bugs.webkit.org/show_bug.cgi?id=324411
- `a89c41295f` `StringToBigInt` now needs at least one digit after a
sign or a radix prefix. `BigInt("-")`, `BigInt(" + ")` and `BigInt("0x
")` throw a `SyntaxError`. They returned `0n` before. `0n == "-"` is now
`false`. https://bugs.webkit.org/show_bug.cgi?id=324127
- `a848db6782` A parenthesized assignment target no longer gives its
name to an anonymous function or class. `(fn) = function () {}` leaves
`fn.name` as `""`. The rule also covers `??=`, `||=`, `&&=` and
destructuring defaults. https://bugs.webkit.org/show_bug.cgi?id=324430
- `ab1caf1170` `JSArray::setLength` skips `countElements()` when the new
length fits in the current vector. A `++array.length` loop past 100000
elements was quadratic. The microbenchmark goes from 2123.65 ms to 5.31
ms. The commit message links
https://github.com/oven-sh/bun/issues/25559.
https://bugs.webkit.org/show_bug.cgi?id=324306
- `433f888ace` `Error.stackTraceLimit = NaN` now clears the internal
limit, and new errors get no `stack`. The old code clamped `NaN` to `0`.
https://bugs.webkit.org/show_bug.cgi?id=323427
- `a0e2a50e76` `sizeOfVarargs()` clamps the `length` of a strict
`arguments` object before it compares it with the argument limit.
`arguments.length = 2 ** 32 + 1; g.apply(null, arguments)` now throws
`RangeError`. https://bugs.webkit.org/show_bug.cgi?id=324226
- `da75c48c45` `ArrayBuffer.prototype.slice` uses the species watchpoint
only when the receiver belongs to the current realm.
`ArrayBuffer.prototype.slice.call(otherRealm.buffer, 0, 8).constructor`
is now `otherRealm.ArrayBuffer`.
https://bugs.webkit.org/show_bug.cgi?id=324619
- `c5c46669ba` `Intl.DateTimeFormat` sets `dayPeriod` only from pattern
characters `b` and `B`, not from the AM/PM marker `a`.
`resolvedOptions().dayPeriod` for `{ hour: "numeric", minute: "2-digit"
}` is now `undefined`. `formatToParts()` still reports the AM/PM marker
as a `dayPeriod` part. https://bugs.webkit.org/show_bug.cgi?id=324559
- `9aea44e083` `Intl.DurationFormat` uses `"always"` as the display
default for minutes and seconds that follow a `"numeric"` or `"2-digit"`
unit. `new Intl.DurationFormat("en", { hours: "numeric" }).format({
hours: 1 })` returns `"1:00:00"`, not `"1"`.
https://bugs.webkit.org/show_bug.cgi?id=324561
- `6319f7420d` `BytecodeGenerator::emitUsingBodyScope()` emits the jump
to `skipSlot` before it ends the try range of each dispose call. DFG
failed in `DFGOSRAvailabilityAnalysisPhase` for some `using` and `await
using` code before. https://bugs.webkit.org/show_bug.cgi?id=324005
- `df94b6ccbb`, `9a38124281` Upstream `JSBigInt` gets Toom-3
multiplication (smaller operand of at least 508 digits) and
Schönhage-Strassen FFT multiplication. Both are ports of V8. The fork
already has both, with the `InterruptCheck` plumbing, so the merge keeps
the fork's versions. https://bugs.webkit.org/show_bug.cgi?id=323587
https://bugs.webkit.org/show_bug.cgi?id=324209
- `d2d61f8871` `JSBigInt` multiplication (`multiplySchoolbook`,
`multiplySpecialLow`, `multiplySpecialHigh`, `multiplyComba` and the
fixed-size variants) uses `std::span` in place of raw pointers. Results
do not change. https://bugs.webkit.org/show_bug.cgi?id=324494
- `ea153e64fb`, `d7240f488f`, `34ccaa804c` `CloneSerializerBase` and
`CloneDeserializerBase` follow JSC throw-scope style and stop at the
first exception. The `jsc` shell adds `structuredClone(value, { transfer
})`. Bun has its own serializer.
https://bugs.webkit.org/show_bug.cgi?id=324423
https://bugs.webkit.org/show_bug.cgi?id=324429
https://bugs.webkit.org/show_bug.cgi?id=324474
- `2a24a9aa7c` `JSClassCreate()` retains
`JSClassDefinition.parentClass`, and the `OpaqueJSClass` destructor
releases it. https://bugs.webkit.org/show_bug.cgi?id=319684
- `8ca47457ed` The new private header `JavaScriptCore/JSStringRefCPP.h`
adds `utf8CString(JSStringRef)` and `createJSString()`.
https://bugs.webkit.org/show_bug.cgi?id=324435
- `18073b9f6c` `JSTypedArrayConstructors.h` declares the explicit
`s_info` specializations for each typed array constructor and for
`JSDataViewConstructor`. Include it before a call to `info()` on these
classes. https://bugs.webkit.org/show_bug.cgi?id=324514
- `125543708a` `TypeProfiler::typeInformationForExpressionAtOffset()` no
longer dereferences a null `TypeLocation`.
https://bugs.webkit.org/show_bug.cgi?id=323314
- `c5fe81278b` `JSObject::crashDueToEmptyValueAtValidOffset` reports new
diagnostic data. The crash reason constant changes to
`0x100900d0ff5e7bad`. https://bugs.webkit.org/show_bug.cgi?id=324194
### RegExp (Yarr)
- `7aeed1e3bd` Non-global `String.prototype.replace(regexp, "")` returns
a substring cell of the subject when the match touches either end.
`string-replace-regexp-strip-prefix` is 2.30x faster.
https://bugs.webkit.org/show_bug.cgi?id=323409
- `ae0a88e6c1` A `\k<name>` back reference in a lookbehind no longer
matches empty when its group is the last group opened.
`/(?<n>.)..(?<=\k<n>.)/.exec("abc")` now returns `null`.
https://bugs.webkit.org/show_bug.cgi?id=324402
- `d8a2cff958` The DFG and FTL anchored first-character filter for
`RegExp.prototype.test` runs only when `lastIndex` is an Int32. Other
`lastIndex` values take the slow path, so the `ToLength(lastIndex)` side
effects stay observable after tier-up.
https://bugs.webkit.org/show_bug.cgi?id=324307
- `d22fa241f1` `SpeculativeJIT::emitRegExpMinimumLengthFilterGuards()`
no longer asserts when base and argument share a register, as in
`re.test(re)`. Debug builds only.
https://bugs.webkit.org/show_bug.cgi?id=324211
### JIT (LLInt, Baseline, DFG, FTL, B3, Air)
- `e57b0d1670` DFG stores OSR exits as a delta-encoded byte stream,
`DFG::OSRExitStream`, and decodes a `DFG::OSRExit` on demand.
`DFG::JITCode::m_osrExit` becomes `m_osrExits`. Exit data in one
JetStream3 run drops from 47.7 MB to 6.3 MB.
https://bugs.webkit.org/show_bug.cgi?id=323407
- `219167e2b4`, `7a5cfe078b` A linked DFG or FTL OSR exit entrance is
now one near call, and the return address identifies the exit. A DFG
entrance shrinks from 8 to 4 bytes on ARM64 and from 11 to 5 bytes on
x86_64. An FTL entrance shrinks from 20 to 4 bytes on ARM64 and from 10
to 5 bytes on x86_64. `DFGOSRExitBase.h` adds `static_assert(isARM64()
|| isX86_64())`. https://bugs.webkit.org/show_bug.cgi?id=324137
https://bugs.webkit.org/show_bug.cgi?id=324407
- `4dbb362ca1` `CodeBlock::updatePredictionsConcurrently()` updates
value profile and array profile predictions without a lock. The Baseline
JIT compiler thread and concurrent GC marking call it, so array profile
updates also move off the main thread.
https://bugs.webkit.org/show_bug.cgi?id=324016
- `418114c05c` `abstractAccess()` calls `entry.prepareToWatch()` when it
resolves a put to a `ClosureVar`. DFG could fold a module variable to a
stale value after an import cycle. This is the upstream form of the
fork's #624, and the merge takes upstream's test files.
https://bugs.webkit.org/show_bug.cgi?id=324124
- `5d1761dffb` DFG SSA lowering emits a separate `CheckInBounds` node
for `StringAt` and `StringCodePointAt`. FTL could remove the bounds
check together with an unused node before. Then `s.codePointAt(i) ===
undefined` stayed `false` for an out-of-bounds `i`.
https://bugs.webkit.org/show_bug.cgi?id=323640
- `54277a51f5` The DFG bytecode parser checks for `BadStringType` exit
sites before it compiles a by-val access as `CheckIdent` plus by-id. A
non-atom key such as `name.toLowerCase()` caused the same OSR exit after
each recompilation. The microbenchmark is 8.03x faster.
https://bugs.webkit.org/show_bug.cgi?id=323839
- `51a07f95fd` The DFG abstract interpreter and the DFG and FTL
`compileSpread()` take the original `Set` structure from the realm of
`node->child1()`. With a cross-realm `Set`, the compiler could treat
`[...set]` as free of side effects.
https://bugs.webkit.org/show_bug.cgi?id=321705
- `4dcc426f83` `B3LowerToAir` checks `crossesInterference()` before it
fuses or moves an `AtomicWeakCAS` or `AtomicStrongCAS` into a later
`Branch` or compare. A wasm `i32.atomic.rmw.cmpxchg` could move past a
`memory.grow` and use a stale memory base.
https://bugs.webkit.org/show_bug.cgi?id=319842
- `9c6d017806` `doneLocation` moves from `PropertyInlineCache` to
`RepatchingPropertyInlineCache`. `HandlerPropertyInlineCache` shrinks
from 88 to 80 bytes. `CodeBlock::findPropertyCache()` no longer exists.
https://bugs.webkit.org/show_bug.cgi?id=324424
- `e87ea0e64e` The specialize-select transform leaves
`B3::ReduceStrength` and becomes the new phase `B3::specializeSelect()`.
The new option `useB3SpecializeSelect` (default `true`) controls it.
https://bugs.webkit.org/show_bug.cgi?id=324673
- `95cec227df`, `7ae08af38b`, `7825a32d2b`, `fda68a8bb0`, `d6cc5eaa35`,
`d7fa43a33f`, `0aad9d201d`, `ba0e7b4024` Compile-time work in Air and
B3: `LiveRange` uses `Vector<Interval, 4>`, `IntervalSet` gets a bulk
constructor, `WTF::Liveness` gets a streaming adapter mode,
`fixObviousSpills` tracks aliased registers in register sets, the dense
liveness budget rises from 4 MB to 8 MB,
`IntervalSet::verifyCoverageConsistency` is a no-op in release builds,
and `B3::Procedure::deleteAllVariables()` is new. Generated code does
not change. https://bugs.webkit.org/show_bug.cgi?id=324009
https://bugs.webkit.org/show_bug.cgi?id=324750
https://bugs.webkit.org/show_bug.cgi?id=324795
https://bugs.webkit.org/show_bug.cgi?id=324695
https://bugs.webkit.org/show_bug.cgi?id=324716
https://bugs.webkit.org/show_bug.cgi?id=324688
https://bugs.webkit.org/show_bug.cgi?id=324759
https://bugs.webkit.org/show_bug.cgi?id=325058
### WebAssembly
- `5ad2bece76` IPInt handler slots shrink from 256 to 128 bytes on
ARM64, and large handlers jump to out-of-line code. offlineasm gains
`bc`, `loadbinc`, `loadbpreinc` and `orlshifti`.
`LowLevelInterpreter.cpp` adds `OFFLINE_ASM_ALIGN_TRAP_128` for Windows
ARM64. The commit message reports about 5% faster IPInt execution.
https://bugs.webkit.org/show_bug.cgi?id=324059
- `b9d477930e` `Heap::finalizeWasmCalleeCleanup()` calls
`WTF::crossModifyingCodeFence()` before it releases Wasm callees.
https://bugs.webkit.org/show_bug.cgi?id=320401
- `778a559d30` Both WasmToJS stubs also store the IPInt `MC` register in
the new `Wasm::WasmToJSIPIntMCSlot`. `Wasm::WasmToJSScratchSpaceSize`
grows from 16 to 32 bytes.
https://bugs.webkit.org/show_bug.cgi?id=324832
- `08f5b5c35e` `JSWebAssemblyInstance::setDebugId()`, `debugId()` and
`m_debugId` exist only under `ENABLE(WEBASSEMBLY_DEBUGGER)`, which
JSCOnly does not set. https://bugs.webkit.org/show_bug.cgi?id=324189
- `f2bd414de3`, `6452e03b9f`, `d8d3577549`, `74efecb8e0`, `a57cde3b59`,
`0aac8dcd47`, `9f9aae3434`, `073031147c` Wasm debugger fixes and the new
`qWasmStackValue` packet. All of this code is under
`ENABLE(WEBASSEMBLY_DEBUGGER)`, which only `PLATFORM(MAC)` sets.
### GC and memory
- `6c0de596d5` `BlockDirectory::findBlockForAllocation()` prefetches the
`MarkedBlock` header before the sweep that builds the free list.
`BlockDirectory::m_blocks` stores `std::pair<MarkedBlock::Handle*,
MarkedBlock*>`. `MarkedBlock::Handle` moves the rarely used `m_weakSet`
behind `m_block`. https://bugs.webkit.org/show_bug.cgi?id=324632
### WTF and bmalloc
- `6c6e928fdc` `WTF::loadLoadFence()` and `WTF::loadStoreFence()` emit
`dmb ishld` on ARM64. They emitted the full `dmb ish` barrier before.
https://bugs.webkit.org/show_bug.cgi?id=324352
- `ce646f1f85`, `3ff034369d`, `2d8b6e5a48`, `95a960a3ae`
`SAFE_WTFLOGALWAYS`, `LOG`, `RELEASE_LOG`, `ASSERT_WITH_MESSAGE` and the
signpost macros convert each argument with `WTF::logPrintfType()`. A
call site can pass a typed C string for `%s`. The helpers move from
`wtf/StdLibExtras.h` to `wtf/Assertions.h`. Existing callers need no
edit. https://bugs.webkit.org/show_bug.cgi?id=324090
https://bugs.webkit.org/show_bug.cgi?id=324142
https://bugs.webkit.org/show_bug.cgi?id=324287
https://bugs.webkit.org/show_bug.cgi?id=324236
- `f83706791b` `CStringWithEncoding::isolatedCopy()` is new.
`CStringBuffer` does not have a thread-safe reference count.
https://bugs.webkit.org/show_bug.cgi?id=319652
- `2d30c8e50c` `StringImpl::simplifyWhiteSpace()` returns `*this`
without allocation when the string is already simplified.
https://bugs.webkit.org/show_bug.cgi?id=324694
- `fbc14a1c5a` `wtf/text/StringCommon.h` adds a SIMD
`countMatchedCharacters()` overload for a compile-time character set.
https://bugs.webkit.org/show_bug.cgi?id=324640
- `77e8645084` `WTF::switchOn()`, `switchOnTupleAtIndex()` and
`WTF::apply()` mark their functor parameters `NOESCAPE`.
https://bugs.webkit.org/show_bug.cgi?id=324320
- `9e74021a2f` `Borrow::~Borrow()` asserts (debug only) that the object
is still borrowed when the borrow ends.
https://bugs.webkit.org/show_bug.cgi?id=324545
- `01f33be1d1` `determineTZoneMallocFallback()` selects
`ForceFastMalloc` when libpas uses MTE (Apple internal SDK on arm64e
only). https://bugs.webkit.org/show_bug.cgi?id=323981
### Build system and platform
- `a2a6f364bf` `WebKitCompilerFlags.cmake` adds `-fwrapv` for GCC, Clang
and `clang-cl` builds when the compiler accepts it. Signed integer
overflow in JSC, WTF and bmalloc code now wraps. Bun compiles its own
C++, which includes JSC inline code, without `-fwrapv`.
https://bugs.webkit.org/show_bug.cgi?id=324351
- `a306abc2c0` `Source/bmalloc/mimalloc/CMakeLists.txt` calls
`add_subdirectory(mimalloc EXCLUDE_FROM_ALL)`. `USE_MIMALLOC=ON` stops
the configure step when CMake is older than 3.25.
https://bugs.webkit.org/show_bug.cgi?id=324458
- `8009ddd215` `wtf/cocoa/MemoryFootprintCocoa.cpp` implements
`memoryFootprint()` with a call to a new overload,
`memoryFootprint(mach_port_t)`. `wtf/MemoryFootprint.h` declares that
overload only under `PLATFORM(COCOA)`, but the JSCOnly port compiles the
file on all Apple targets. The fork widens the guard to `OS(DARWIN)`.
https://bugs.webkit.org/show_bug.cgi?id=323690
- `fd4a9d09bf` `WebKitCommon.cmake` sets
`CMAKE_POSITION_INDEPENDENT_CODE` only when `NOT APPLE`. The fork keeps
its `NOT USE_BUN_JSC_ADDITIONS` condition as well.
https://bugs.webkit.org/show_bug.cgi?id=325064
- `5a819a7b96`, `d00124d9d7`, `6f39f11c5e` `WebKitCommon.cmake` records
the build settings with `set-webkit-configuration` when the build
directory is under the WebKit product directory. The step is not fatal,
and Bun's build directory does not match.
https://bugs.webkit.org/show_bug.cgi?id=324135
https://bugs.webkit.org/show_bug.cgi?id=324558
https://bugs.webkit.org/show_bug.cgi?id=324648
- `5bb1c6d49c` `WebKitCommon.cmake` derives `WTF_CPU_*` from
`CMAKE_OSX_ARCHITECTURES` on Apple hosts when that variable names one
architecture. This corrects an x86_64 build on an arm64 Mac, including
the offlineasm backend choice.
https://bugs.webkit.org/show_bug.cgi?id=319646
- `94ff070fff` `_WEBKIT_ADD_CODE_SIGN` reads entitlements from the
`CODE_SIGN_ENTITLEMENTS` target property. The fork keeps its early
`return()` for `CMAKE_CROSSCOMPILING`.
https://bugs.webkit.org/show_bug.cgi?id=324292
- `5cc3f23625` `WebKitCompilerFlags.cmake` no longer sets
`CMAKE_COMPILE_WARNING_AS_ERROR` for `DEVELOPER_MODE` builds on Windows.
https://bugs.webkit.org/show_bug.cgi?id=324157
- `61b575f0d0`, `2834de45ef`, `78c1083fa2`, `27504b2544` Build fixes and
one removed CMake option (`ENABLE_SWIFT_DEMO_URI_SCHEME`). No effect on
a JSCOnly build.
### Reverted within the range
- `b34e745e23` Upstream reverts the Linux main-thread detection from
317619@main (`getpid() == gettid()`), which aborted hosts that start WTF
on another thread. The fork had disabled that path under
`USE(BUN_JSC_ADDITIONS)`. The merge drops the fork's guards.
https://bugs.webkit.org/show_bug.cgi?id=322394
- `6ba0c9f709` and `d6e6a0fc1f` (`wtf/EscapableByteSpan.h`),
`14d632bf1e`, `0d533fd7f0` and `4dbba08d80` (Xcode PGO settings),
`d6f958d63e`, `e13c60e3d5` and `5a1e7b740f` (a web preference),
`3f7093e05c` (a web preference). No net effect on JSC.
### WebCore-only or no effect on a JSC embedder
`0d729748ef`, `162c4db3f1`, `a91d249a05`, `bf4e2de4fd`, `4ebc2a99c1`,
`3e95a187a1`, `648bbc69d1`, `3e1e77d2ba`, `a0df39e48d`, `fa1ff79d59`,
`27621d5adf`, `56909e17f9`, `d49b603f37`, `55f5311df8`, `13d5142b78`,
`484abf80fd`, `e887d63b22`, `d07436ebd4`, `49649b12d8`, `6307d48da4`,
`1aa6a33856`, `d0755e594a`, `7c5bf4eb1f`, `6b34ce7a2b`, `9c43b4a109`,
`56677f10e9`, `e25f645b0f`, `5fa37cf1fa`, `12a60d1a39`, `88ebf35179`,
`fc260f4e1c`, `263f9383d1`, `a749c7f864`, `d9eaeec654`, `06c8bf6974`,
`1666648452`, `a7c26d671b`, `6c721682be`, `3a633e3e57`, `02ad1221be`,
`36a3ac72aa`, `3113b23fc2`, `9467789fc1`, `41a9dfe94e`, `0ac65b1a46`.
</details>
<details><summary>Upstream changes, ccdcb8a026..6b58d86abe (216 commits,
47 touch JavaScriptCore, WTF, bmalloc, cmake or JSTests)</summary>
#42666 has the full list for this part of the range (runtime, GC,
RegExp, JIT, WebAssembly, WTF and build changes). These are its entries
that need an embedder-side change or a check.
Each entry says what a caller must change. Some entries need a check
only, and say so.
- `74b519d7f9` `WTF::String(std::span<const char>)` is now private, next
to `String(const char*)`, because `char` carries no encoding. Callers
name the encoding: `String::fromLatin1(std::span<const char>)` (new
overload), `String(std::span<const Latin1Character>)`,
`String::fromUTF8(...)` or `String(ASCIILiteral)`. In the same commit
`WTF::enumName()` and `WTF::enumTypeName()` (`wtf/EnumTraits.h`) return
`ASCIILiteral`. They returned `std::span<const char>` before, so callers
now test `isEmpty()` and not `empty()`.
https://bugs.webkit.org/show_bug.cgi?id=323650
- `7bd7b6dfad` `CString` gains `legacyCStringPointer()`, which returns
the same `const char*` as `data()`. Every upstream `utf8().data()` call
site moves to it. `CStringWithEncoding::characters()` (the `const char*`
accessor of `UTF8CString` and `ASCIICString` from `5f14e32e57`) is
renamed to `legacyCStringPointer()`. No type changes in this commit. It
is the mechanical half of the retype of `String::utf8()`. The retype
itself is `00130dc2f3`, the next entry.
https://bugs.webkit.org/show_bug.cgi?id=323722
- `00130dc2f3` `String::utf8()`, `StringImpl::utf8()`,
`StringView::utf8()` and `Identifier::utf8()` now return `UTF8CString`.
They returned `CString` before. `UTF8CString` is the alias
`CStringWithEncoding<char8_t>` (alias in `wtf/Forward.h`, class in
`wtf/text/CString.h`). The siblings are `Latin1CString`
(`Latin1Character`) and `ASCIICString` (`char`). `CStringWithEncoding`
is a final class that derives publicly from `CString` and adds no data
member. It hides the `CString` accessors so that the character type
carries the encoding. `data()` still exists, but for a `UTF8CString` it
returns `const char8_t*`. `span()` and `spanIncludingNullTerminator()`
return `std::span<const char8_t>`, and `mutableSpan()` returns
`std::span<char8_t>`. `legacyCStringPointer()` returns the same address
as `const char*`. It is the accessor for `%s` arguments and C functions,
and `Latin1CString` does not have it. `length()`, `isNull()`,
`isEmpty()`, `hash()` and `toStdString()` come from `CString` and do not
change. A call such as `s.utf8().data()` that feeds a `const char*`
parameter must become `s.utf8().legacyCStringPointer()`. The same
applies to `s.utf8().span().data()`. For a `std::span<const char>`,
write `byteCast<char>(utf8.span())`. A `const void*` parameter
(`fwrite`, `write`) still accepts `data()`. The `SAFE_PRINTF` and
`SAFE_FPRINTF` macros accept the `UTF8CString` itself. `PrintStream` has
no overload for `const char8_t*`, so `dataLog()` must get the
`UTF8CString` itself or the `String`. A `UTF8CString` converts
implicitly to `CString` (derived to base). So `CString c = s.utf8()`
still compiles and `c.data()` is `const char*`, but the encoding is
lost. `String` gains an implicit constructor from `const
CStringWithEncoding<CharacterType>&` that decodes by character type.
`CStringWithEncoding` gains explicit constructors from `const
std::string&` and from a null-terminated `const CharacterType*`.
`wtf/text/StringCommon.h` gains `unsafeSpan(const char8_t*)`.
https://bugs.webkit.org/show_bug.cgi?id=323846
- `9b09294076` Upstream removes about 850 `legacyCStringPointer()` call
sites where the destination already accepts a `String`. `LOG` with `%s`
becomes `LOG_WITH_STREAM`, `EXPECT_STREQ` becomes `EXPECT_EQ` in tests,
and `dataLog()` gets the `String`. Almost all edits are in WebCore,
WebKit and TestWebKitAPI. In JSC and WTF the commit edits two lines.
`Options::dumpAllOptions()` and the truncation path of
`printInternal(PrintStream&, const CString&)` now print a `String`
directly. No WTF or JSC function changes a parameter type or a return
type. No caller edit is needed.
https://bugs.webkit.org/show_bug.cgi?id=323859
- `7189f73167` `StringPrintStream::toCString()` is renamed to
`toUTF8CString()` and returns `UTF8CString`. The function template
`WTF::toCString(...)` is renamed to `WTF::toUTF8CString(...)` in the
same way. The old names have no alias. `printInternal(PrintStream&,
const CString&)` is now `= delete`, and the non-const `CString&`
overload is removed. So `out.print(cstring)`, `dataLog(cstring)` and
`dataLogLn(cstring)` do not compile for an untyped `CString`. New
overloads print `const UTF8CString&`, `const ASCIICString&` and `const
Latin1CString&`. UTF-8 and ASCII bytes go through unchanged, and Latin-1
is transcoded to UTF-8. To replace `out.print(someCString)`, keep the
typed value (`auto s = string.utf8()`, `toUTF8CString(...)`,
`string.ascii()`) and print that. Or print the `String` or `StringView`
itself, or pass `cstring.data()` as `const char*`. These bytecode
helpers now return `UTF8CString`: `CodeBlock::inferredName()`,
`CodeBlock::sourceCodeForTools()`, `CodeBlock::sourceCodeOnOneLine()`,
`InlineCallFrame::inferredName()`, `UnlinkedSourceCode::toUTF8()`,
`reduceWhitespace()`, `ArrayProfile::briefDescription()`,
`ValueProfile::briefDescription()`, `BytecodeDumper::registerName()` and
`constantName()`. These JIT and runtime helpers do the same:
`MacroAssemblerCodeRef::disassembly()`, `Compilation::disassembly()`,
`ExceptionScope::unexpectedExceptionMessage()`, `Air::Special::name()`,
`JITPlan::signpostMessage()`, `Wasm::Plan::signpostMessage()`,
`DFG::nodeListDump()`, `nodeMapDump()` and `nodeValuePairListDump()`. In
WTF, `sortedListDump()`, `sortedMapDump()`, `BackwardsGraph::dump()`,
`SingleRootGraph::dump()` and `StringHashDumpContext::brief()` return
`UTF8CString`. `Identifier::ascii()` and
`StringHashDumpContext::getID()` return `ASCIICString`, and
`Structure::dumpBrief()` takes `const ASCIICString&`. `PerfLog::log()`,
`GdbJIT::log()`, `Profiler::Database::logEvent()` and
`Profiler::Compilation::addDescription()` take `const UTF8CString&`, and
`DFG::validate()` takes a `UTF8CString`. As a side effect
`CodeBlock::inferredNameWithHash()`,
`SamplingProfiler::reportTopBytecodes()` and
`DebuggerCallFrame::functionName()` no longer decode UTF-8 function
names as Latin-1. https://bugs.webkit.org/show_bug.cgi?id=323960
- `25f7ce345a` `FileSystem::fileSystemRepresentation(const String&)`
returns `UTF8CString`. It returned `CString` before. A caller that
passed `.data()` to `open()`, `stat()` or a similar C function must call
`.legacyCStringPointer()`. On Windows the function now converts with
`CP_UTF8`. It converted with `CP_ACP` (the active ANSI code page)
before. The GLib functions `currentExecutablePath()`,
`currentExecutableName()` and `webkitTopLevelDirectory()` also return
`UTF8CString`, and Cocoa gains `currentExecutableName()`.
`createTemporaryFileInDirectory()` (Cocoa only) returns
`std::pair<FileHandle, String>`. `wtf/StdLibExtras.h` gains
`safeNSStringPrintfType()` and the `SAFE_WTFLOGALWAYS` macro.
`CStringWithEncoding` gains `createNSString()` for Objective-C++ code.
The JSC callers (`dumpJITMemory()`, `API/JSScript.mm`) move to
`legacyCStringPointer()`. https://bugs.webkit.org/show_bug.cgi?id=324034
- `8ae0649a80` `WeakGCMap<Key, Value>` now stores a raw `Value*` per
entry. It stored a `Weak<Value>` before, which is a pointer to a
separate `WeakImpl` that the heap reaps in each collection. `ValueType`
is `ValueArg*`. So `set(key, value)` takes a raw pointer, and the
`ensureValue()` functor returns a raw pointer. `find()->value` is a raw
pointer with no `.get()`. `isEmpty()` is removed. `pruneStaleEntries()`
is replaced by `reconcileWeakReferencesAtGCEnd(VM&, CollectionScope)`.
`WeakGCMap.h` no longer includes `Weak.h`, and `WeakGCMapInlines.h` no
longer includes `WeakInlines.h`. A caller that wrote `map.set(key,
Weak<T>(cell))` must write `map.set(key, cell)`. A file that got
`JSC::Weak` through `WeakGCMap.h` must include `<JavaScriptCore/Weak.h>`
itself. Old design: `WeakBlock::reap` cleared each `Weak<>` in every
collection, and `pruneStaleEntries()` removed the cleared entries in
full collections only. New design: `Heap::runEndPhase()` calls
`Heap::reconcileWeakGCHashTables()`, and each table tests its values
with `Heap::isMarked()`. A full collection visits every registered table
and removes each entry whose value is null or not marked. An eden
collection visits only the tables on the new list
`Heap::m_dirtyWeakGCHashTables`. `set()` and `ensureValue()` put the map
on that list through `WeakGCHashTable::markDirty(VM&)`. In an eden
collection the map only sets a dead value to null and does not rehash.
`get()`, `find()`, `contains()` and `ensureValue()` treat the null entry
as absent, and the next full collection removes it. A table that gained
no entry since the last collection is skipped. All its values are old,
and an eden collection cannot free them. `WeakGCHashTable`
(`runtime/WeakGCHashTable.h`) now derives from
`BasicRawSentinelNode<WeakGCHashTable>`. A subclass must override
`reconcileWeakReferencesAtGCEnd(VM&, CollectionScope)` in place of
`pruneStaleEntries()`. It must call `markDirty(vm)` when it adds an
entry, if eden collections must visit it.
`Heap::unregisterWeakGCHashTable()` also takes the table off the dirty
list. `WeakGCSet` keeps `Weak<>` entries and removes them in full
collections only, as before.
https://bugs.webkit.org/show_bug.cgi?id=323958
- `b8d7e24add` The MarkedBlock warm-up (prefault) supply moves from JSC
into libpas. The old code was `WarmUpBlockProvider` in
`heap/FastMallocAlignedMemoryAllocator.cpp`. It ran a `JSCWarmUp`
`AutomaticThread` that allocated blocks with
`tryFastCompactAlignedMalloc()` and wrote one byte per page. It worked
with every `fastMalloc` backend. The new code is
`bmalloc_prefault_supply.c` and `bmalloc_prefault_supply.h` in libpas,
and JSC calls it only under `#if USE(LIBPAS)`. So upstream, a build
whose `fastMalloc` is mimalloc or the system allocator gets no
prefaulted blocks. In that build `tryAllocateAlignedMemory()` calls
`tryFastCompactAlignedMalloc()` directly. With libpas,
`tryAllocateAlignedMemory()` returns
`bmalloc_prefault_supply_try_allocate()` for block-sized requests. The
supply is a fixed array of at most 64 slots
(`BMALLOC_PREFAULT_SUPPLY_MAX_BLOCKS`). Takers and the filler exchange
slots with atomic operations and no lock. A mutex and a condition
variable only wake or start the filler. The filler is a detached
pthread. It allocates with
`bmalloc_try_allocate_with_alignment_inline()` and touches pages with
the new `pas_page_malloc_populate()`. After one idle interval with no
demand it frees all blocks and exits, and a later take starts a new
thread. The options `useWarmUpMarkedBlocks` (true),
`warmUpMarkedBlockCount` (32) and `warmUpMarkedBlockIdleTimeout` (10
seconds) keep their names and defaults. JSC copies them once into
`bmalloc_prefault_supply_target` and
`bmalloc_prefault_supply_idle_timeout_in_milliseconds`.
`$vm.warmUpMarkedBlockState()` is removed.
`$vm.warmUpMarkedBlocksAreEnabled()` and `$vm.warmUpMarkedBlockCount()`
replace it, and `$vm.setWarmUpMarkedBlockAllocationShouldFail()` stays.
In C++, `warmUpMarkedBlockStateForTesting()`, `WarmUpMarkedBlockPhase`
and `WarmUpMarkedBlockState` are removed.
`warmUpMarkedBlocksAreEnabledForTesting()` and
`warmUpMarkedBlockCountForTesting()` are added, and without libpas they
return `false` and 0. `pas_thread.h` (the Windows pthread shim) gains
include guards, `PTHREAD_MUTEX_INITIALIZER`, `PTHREAD_COND_INITIALIZER`,
`extern "C"` and `PAS_API` exports. The new source file is listed in
`Source/bmalloc/CMakeLists.txt` and
`Source/bmalloc/libpas/CMakeLists.txt`.
https://bugs.webkit.org/show_bug.cgi?id=323480
- `2aedf51ba6` `WTF::UUID::emptyValue` and `UUID::deletedValue` become
private. The constructor `UUID(HashTableEmptyValueType)` becomes private
too. Only `HashTraits<UUID>` and `MarkableTraits<UUID>` (now friends)
can build the empty value. `UUID(HashTableDeletedValueType)` stays
public. `UUID(UInt128)` now release-asserts that the value is not 0
(empty) and not 1 (deleted), so `UUID { 0 }` crashes. `UUID(uint64_t
high, uint64_t low)` now rejects the empty value as well as the deleted
value. Code that needs "no UUID" must use `Markable<WTF::UUID>` or
`std::optional<WTF::UUID>`. `createVersion4()`, `createVersion4Weak()`,
`createVersion5()`, `parse()`, `parseVersion4()` and `toString()` do not
change. https://bugs.webkit.org/show_bug.cgi?id=323944
- `a371ed3141` A caller can no longer construct a `WTF::UUID` from raw
bits. `UUID(std::span<const uint8_t, 16>)` and `UUID(UInt128)` become
private. `UUID(std::span<const uint8_t>)` and `UUID(uint64_t, uint64_t)`
are removed. New factories replace them. `static std::optional<UUID>
tryCreate(std::span<const uint8_t>)` returns `std::nullopt` if the size
is not 16 or the value is reserved (0 or 1). `static std::optional<UUID>
tryCreate(uint64_t high, uint64_t low)` does the same for two halves.
`static consteval UUID createConstant(uint64_t high, uint64_t low)` is
for hardcoded constants, and a reserved value is a compile error. The
static `UUID::isValid(uint64_t, uint64_t)` is removed, and the member
`isValid()` stays. The only raw constructor call in JSC
(`jscJITNamespace` in `jit/ExecutableAllocator.cpp`, under
`HAVE(KDEBUG_H)`) moves to `createConstant()`. The random, parse and
string functions do not change. A caller that only uses
`createVersion4()`, `createVersion4UUIDString()`, `parse()` or
`toString()` needs no edit.
https://bugs.webkit.org/show_bug.cgi?id=324032
- `2d4a4717af` `wtf/UUID.h` gains the struct `UUIDCanonicalForm` (two
`uint64_t` fields, `high` and `low`) and
`StringTypeAdapter<UUIDCanonicalForm>`. The adapter holds the 8-4-4-4-12
lowercase hex layout. `StringTypeAdapter<UUID>` now derives from it and
passes `uuid.high()` and `uuid.low()`. The output of `makeString(uuid)`
does not change. The only new user is the FIDO AAGUID logging in WebKit.
No caller edit is needed. https://bugs.webkit.org/show_bug.cgi?id=324075
- `6103d1b95a` `makeStringByJoining(std::span<const String>, …
Jarred-Sumner
added a commit
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Oct 2, 2026
main has the upgrade to upstream WebKit 7b485a7 (#725) and source positions that are offsets only (321541@main, #734). Positions. A line and column are no longer kept in ExpressionInfo, in a function executable or in a SourceCode. They are worked out from an offset by the SourceProvider's LineStartTable. While a static heap is built its providers do not exist yet, so nothing there can ask one. - StaticHeap::build() has a LineStartTable of its own for each module and builtin, filled from the line starts that come with the code, and passes it down to makePositions(). - Code comes without line starts if its source is under 1,024 characters, because such a text is scanned as cheaply. The heap's builder has no text to scan: VM::BytecodeGenerationOptions::keepLineStartsOfEverySource, for a VM that generates bytecode to be compiled ahead of time. - A module's code block stays in the heap, and gives its line starts to the provider at run time. They are borrowed from the payload, so it gets a copy of them in the heap's data. Without bytecode it needs none: every position then comes from makePositions(). - ExpressionInfo::lineColumnInTextForInstPC() remembers its results, as lineColumnForInstPC() did. It must not when it is in the static heap, which may be read-only. - The SourceCode that is made up for a short-form executable can no longer say where the function starts, so FunctionExecutable::firstLine() asks ScriptExecutable, which knows about the short form. - A builtin is encoded when the embedder is built, so one under 1,024 characters has no line starts in the heap. Its positions are all on its first line. UnlinkedFunctionExecutable is 16 bytes smaller, and whatIsSharedByStaticExecutables() no longer states its size. The rest is names: toCString() is toUTF8CString(), an option that is a string is a const char8_t*, the names of marking constraints are ASCIILiterals.
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Problem
Since the upgrade to upstream
7b485a76e9, code stores source offsets only, and a line and column come from the source'sLineStartTable.error.stacktakes 2.5 ms, and took 0.02 ms before the upgrade. Code that runs from cached bytecode never reads its text otherwise, so for a 100 MB module in abun build --compile --bytecodeexecutable that read takes 30 ms and adds 137 MB of RSS.ExpressionInfo's cache together with the line and column fields. A stack with a frame after 1,000 statements of its function takes 17.8 µs to read, and took 2.3 µs.SourceCodeno longer has a first line.at map (native:1:11)becameat map (native:3323:11),error.lineof an error thrown in a builtin changed the same way, and the first such position scans that text.Change
Whoever makes the code makes the table, and nothing scans a source that is parsed.
shiftLineTerminator(), and the parser gives the list to the source when the parse has succeeded. That is all that changes in the lexer and the parser. Tokens, nodes, expression info and bytecode stay as upstream left them.CodeCacheor out of bytecode, gets the table from the code. In the bytecode it is in the last region, with the expression info, and is borrowed from a payload that stays mapped.LineStartTable::build(), which is unchanged. That is a source under 1,024 characters (a table costs an allocation and a few reference counts whatever its size), theFunctionconstructor, a builtin with a source of its own that is not run from bytecode, and a syntax error.cachedTypesFormatRevisionis 12.documentLineColumnForOffset()also computed the end of the line, which reads the characters before it, and dropped the result.ExpressionInfo::lineColumnInTextForInstPC()keeps each position it computed, in a map from instruction to line and column like the one upstream removed. What it keeps is the position in the text. Sources share unlinked code when theCodeCachefinds their text equal, and everyone who asks it for global code gives it all of a source, so that position is the same for every source that shares the code, and the only miss is the first time an instruction is asked about. Where a source says its text starts (lineOffsetinnode:vm, an inline<script>) is added by the caller.Options::useSourceCodeDump(), useCodeBlock::lineColumnForBytecodeIndexConcurrently(), which keeps nothing. The collector asks only in phases where the mutator is stopped. A lock cost 9 to 12 ns per frame (2%) and 8 bytes perExpressionInfo.BuiltinsSourceProvideris the text of many builtins, one after the other, and is told where each starts. A position in it counts from the start of its builtin, as before the upgrade, closures inside a builtin included. It takes no table.Testing
line-start-table-positions.jscompares positions with ones counted a character at a time. It covers LF, CR LF, CR, a mix, and U+2028 / U+2029 in a 16-bit source; a first line of exactly 127, 128, 16,383, 16,384, 2,097,151 and 2,097,152 characters; line counts around the block size; the line of a syntax error; and line terminators inside a token (a comment, a template, a line continuation, U+2028 and U+2029 in a string), at the top level and, but for the last, in a function.line-start-table-comes-with-the-code.jstakes the place ofline-start-table-not-built-by-ordinary-parse.js, which said the opposite. It also runs through the bytecode cache, with a copied and with a borrowed payload: in the second run the file is not parsed.builtin-position-counts-from-the-builtin.js.run-builtins-generator-testspasses, with four expectations updated for the new array.node:vm, twovm.Scripts with the same text and differentlineOffsets, and the frames of builtins (native:1:11,native:19:34,processTicksAndRejections (native:7:39)).check-webkit-stylereports nothing for the change.Measurements
Linux x64, release builds of Bun with LTO. "Before" is the fork before the upgrade (
35e8970dfd), "main" is the fork's main (74650443cb). Medians.First
error.stackin a file that is run, in µs:First
error.stackin abun build --compileexecutable whose one module is 100 MB of source before bundling:--minify--bytecode--minify --bytecodeOne
new Error().stack, repeated, in µs:Over 22 such cases this PR is between 0.95 and 1.05 of "before". The "main" column is from an earlier run. Stacks of 100 frames, in ns per frame: 479 before and 474 here on one thread, 570 and 549 in 16 workers at once, 493 and 490 with the sampling profiler on.
Loading and the first stack trace have not been measured again since the lexer took the place of a scan at compile time. An earlier revision, whose lexer did the same and more, loaded a module of 1.5 KB to 12 KB in 2% to 3% fewer instructions than "before".
A stack trace whose call sites are all new, so that nothing is kept yet, in instructions:
That is the lookup in the table, which the code did not need when it had its lines and columns. With checked spans and
WTF::LEBDecoderit was +9% and +20%.What an executable embeds (source and bytecode, without the runtime), in MB:
tsc, plaintsc,--bytecodetsc,--minify --bytecode--bytecode